The invention relates to an apparatus for inserting mold filled with a monomer mixture into rotating polymerization columns, by means of an alternating pushing and release of a column of moulds falling down from tubular magazines connected to the said polymerization column. This apparatus is applied especially for the production of contact lenses.
In the continuous centrifugal casting of contact lenses or other articles by polymerizing monomeric mixtures which are dosed into casting molds in advance, it is necessary to substantially removed oxygen from the molds which are advanced into a polymerization zone of the rotating column by flushing with an inert gas. This objective may best be achieved by a gradual release of individual molds containing a monomer mixture from their magazines while permitting the released molds, to fall freely into an upper empty section of the column against a flow of inert gas. The molds, while they are in their magazines and during their individual insertion therein as well, should be continuously kept in a rotating motion which prevents the monomeric mixture from flowing down from the circumference of the casting mold. In addition to complex mechanical systems which employ common construction elements, a relatively simple device is known wherein the gradual release of individual molds from the rotating tubular magazine is achieved by an alternating closing and releasing of springs positioned above the inlet of the column. This device complies with the required tasks but it has a rather high failure rate due to the fatigue of the springs which are very much stressed and become periodically deformed. This prior art mechanism also slowed down the column rotation in an unpredictable way thus causing fluctuation of its rotational speed.